Sums that Go Over to the Next Ten

This is a complete lesson with instruction and exercises about sums that "go over" or cross the next ten, meant for 2nd grade. First, students use visual models (base ten blocks) to add a single digit number and a two-digit number where the sum exceeds the next whole ten (such as 28 + 5). The idea is to notice that these sums are similar to single-digit addition facts. Then they do the same without visual models, breaking down the single-digit number into two parts (first part completes the ten). The lesson also contains word problems and pattern exercises.

Sums that go over to the next ten

Let's add 59 + 5 so that we first complete 60.

59 + 5
| \59 + 1 + 4

60
+ 4 = 64

The 5 is broken into two parts: 1 and 4.
That is because 59 and 1 makes sixty.
Then, we have 60 and 4. We get 64.

9 and 1 make a ten.
We get 6 tens.

59 + 5 = 64

1. Circle ten little cubes to make a ten. Count the tens and ones. Write the answer.

a. 13 + 9 = ______

b. 15 + 8 = ______

c. 17 + 7 = ______

d. 24 + 7 = ______

e. 25 + 6 = ______

f. 37 + 9 = ______

g. 36 + 6 = ______

h. 48 + 4 = ______

i. 58 + 5 = ______

2.
Complete. Break the second number into two parts so that you complete the next
ten.

a. 28 + 8
/ \

28 + 2
+ ____

30
+ ____ = ______

b. 47 + 5
/ \

47 + 3 + ____

50 + ____ = ______

c. 79 + 9
/ \

79 + ____ + ____

80 +
____ = ______

d. 39
+ 3
/ \

39 + ____ + ____

40 + ____ = ______

e.
27 + 5
/ \

27 + ____ + ____

______ + ____ = _____

f. 38 +
7
/ \

38 + ____ + ____

______ +
____ = _____

3. Write
the additions that the number line pictures illustrate. Think how long each line
is.

a. ____ + ____ = ________

b. ____ + ____ = ________

4.
Show these additions on the number line by drawing two lines.

a.
19 + 7 = _____

b. 14 +
18 = _____

5. Solve the problems. Write a number sentence for each
problem, not just the answer.

a. Benjamin wants to buy a
kite that costs $30.
He has saved $22.
How much more money will he need?

b.
Natasha
had already saved $20. She earned $5 by
selling eggs, and earned $5 more for selling fruit.
How much
money does she have now?

c.
Mom bought 28 fruit trees and has planted
eight of them. How
many still need planted?

d. Thirty-seven people attended Uncle
Sam's
50th birthday party.
Thirty-two of them came
before noon. How many came after noon?

e.
Dad bought a bunch of 40 grapes and ate half of them.
Then, little sister ate seven grapes. How many are left
now?

6. Continue the patterns. COMPARE the columns, and NOTICE what is the same.

How to set up algebraic equations to match word problems
Students often have problems setting up an equation for a word problem in algebra. To do that, they need to see the RELATIONSHIP between the different quantities in the problem. This article explains some of those relationships.